Both the BMW M4 GT3 and Ford Mustang GT3 have been hit with power reductions as part of a revised Balance of Performance for next weekend’s Battle on the Bricks at Indianapolis Motor Speedway.
Released on Wednesday, the BMW, which won last month’s Michelin GT Challenge at VIR, faces a 5 kW (6.7 horsepower) reduction for The Brickyard, while the Ford has a more severe 6.6 kW (8.8 hp) power cut through a 1 mm smaller air restrictor.
Additionally, the Acura NSX GT3 Evo22 has also been pegged back, to the tune of 8.5 kW (11.4 hp).
The only GT3 car to receive a power increase is the Mercedes-AMG GT3 Evo, which gains 5 kW (6.7 hp) through a 0.5 mm larger air restrictor.
IMSA has also tweaked the BoP for the GTP class, with the championship-leading Porsche 963 getting a 3 kg increase in minimum weight since the last round at Road America, while the BMW M Hybrid V8 will be up 2 kg, the Acura ARX-06 receiving 1 kg of additional ballast and no weight change for the Cadillac V-Series.R.
In terms of power, BMW has the largest increase at 7 kW (9.4 hp), with Porsche getting a 6 kW boost (8 hp), the Cadillac with 5 kW (6.7 hp) more power and no change to the Acura, which remains maxed out at 520 kW.
The Lamborghini SC63, which returns for the first time since Watkins Glen, meanwhile, has been set with a minimum weight of 1030 kg and power output of 518 kW.
This puts it in a similar weight level to the BMW but at maximum power that’s closest to the Cadillac.